NEET Kunoichi to Nazeka Dousei Hajimemashita

Tsukasa Atsumi is a salaryman who leads an ordinary, solitary life. On his way back from work one evening, he is saved from a demon attack by a mysterious woman in a ninja outfit. Introducing herself as Shizuri Ideura, she claims that demons target people like Tsukasa, who have Samurai Blood in their veins, and that her kind have been protecting them from the shadows.